The word “art” floats in a caricature cloud above the road withinside the architect’s sketchbook, on show withinside the new 305m (209m) extension to the San Francisco Museum of Modern Art. “Environmental concept”, reads a scribbled observe at the page. “Fog.”

Norwegian architects Snøhetta, designers of the chiselled 10-storey addition to SFMOMA, because of open to the general public on 14 May, are fond in their herbal metaphors. They speak in their outstanding opera residence in Oslo as an iceberg, their cultural centre deliberate for the deserts of Saudi Arabia as a pile of pebbles, even as right here in San Francisco they have got tried to conjure some thing as mild and vaporous because the city’s well-known coastal mists.

Fog is not the primary component that springs to thoughts whilst you stumble upon the rippling white cliff face that now looms in the back of the museum’s authentic home, constructed in 1995 through Swiss po-mo maestro Mario Botta. It seems greater like a significant meringue, a constructing-sized baked alaska slumped at the skyline among Botta’s weighty temple and the fashionable Art Deco tower of the Pacific Bell constructing in the back of.

“We desired some thing tons lighter, greater open and obvious than our present home,” says Neal Benezra, director of the museum due to the fact 2002. “Botta gave us this big, muscular, iconic presence that we wanted while we first moved right here, to what turned into then pretty a run-down neighbourhood, however instances have changed. Back then, a museum’s essential position turned into approximately looking after and protective the art, however this century it is tons greater approximately the traveler experience.”

The significant new extension nearly triples the museum’s show location to 175,000 rectangular feet (16,250 rectangular metres) – offering 40% greater gallery area than even the Museum of Modern Art in New York – organized as a stack of flooring in the back of the prevailing constructing, wrapped in an amorphous shell that bulges out round its midriff, as a way to match greater floorspace at the exceedingly slender lot.

Clad in undulating panels of white fibre-strengthened polymer, that are meant to bear in mind each fog and the rippling water withinside the bay, the constructing has a inescapable flimsiness, as though has been carved from polystyrene just like the architectural fashions on show inside. The shape is sliced flat in which it meets the road, growing a shear surface “like a rock cracked open”, say the architects; however, clad with back-painted white glass, it as an alternative provides the dumb elevation of a everyday branch store. Compared to the cautiously particular brickwork and banded granite blocks of the Botta constructing subsequent door, the whole lot feels a chunk inexpensive, in each fabric high-satisfactory and architectural thinking.

The homes could not be greater different, or higher reflections in their respective eras, and the pair do now no longer make a especially glad marriage. Indeed, after touring the conjoined complex, it makes you surprise why one turned into deferentially saved on the rate of the opposite, even as being drastically lobotomised withinside the process.

Botta’s stately museum squares as much as Third Street with an enforcing presence, status as a stepped brick ziggurat from which a ambitious zebra-striped cylinder emerges, sliced at a pointy attitude to shape a hanging cyclopean oculus. With a robust primary axis of symmetry, the layout sampled the whole lot from Louis Kahn to Siena Cathedral, ushering gallery-goers in via a definitely momentous front sequence. At the lowest of the mild-overflow cylindrical atrium, site visitors have been funnelled into an enclosed staircase of darkish granite, difficult and polished in alternating bands, a theatrical threshold that had the drama of getting into a pharaoh’s pyramid.

All this has been swept away. In region of Botta’s cosmic portal now stands an open wood stair, angled off-centre and growing in a jaunty dog-leg. The impact is like erecting an Ikea flat-percent in a temple, the blonde timber jarring with the weighty granite columns. The museum says that the authentic stair turned into too slender to satisfy the projected growth in traveler numbers, and that they desired to open up a visible connection to the brand new lobby beyond – which, accessed through its very own front stair from the opposite road, makes Botta’s foyer sense saggy and redundant.

The Ikea flatpack sensibility keeps withinside the new constructing, in which a international of greater blonde maple and now no longer especially well-crafted info unfolds. It has the in rudely Scandi fashion of a present day high-road garb store (a Gap flagship perhaps), which won’t come as any such surprise, for the reason that number one reason of the extension is to residence the donation of the 1,000-robust series of Doris and Donald Fisher – founders of Gap.

It is a significant quantity of area, full of 19 separate exhibitions for the hole season, which makes seeing the whole lot in a single move pretty an ordeal. It is a marathon adventure it’s now no longer especially helped through the relentless uniformity of the galleries, none of which revel in herbal mild or perspectives to the out of doors international. Moments of respite are luckily furnished withinside the move location alongside the constructing’s northern flank, in which regularly narrowing staircases upward thrust among landings with deep window seats and perspectives out to the city, even as more than one sculpture terraces additionally carry a chunk of variety, certainly considered one among them offering the dramatic feeling of edging alongside the aspect of a glacier.